The present invention relates to aqueous ink. More particularly, it relates to ink suitable for ink-jet recording system.
Heretofore, in the ink-jet recording system, there has been used ink obtained by dissolving a water-soluble dye in water or a mixed solution of water and a water-soluble organic solvent (hereinafter referred to as an "aqueous medium", generically). However, since the water-soluble dye is essentially inferior in water resistance and light resistance, a fastness of a recorded image sometimes become a problem.
Therefore, in order to use a water-insoluble colorant which is superior in fastness, particularly water and light resistances, such as pigment (e.g. carbon black, etc.), water-insoluble dye (e.g. disperse dye, oil-soluble dye, etc.) and the like in place of the water-soluble dye, various dispersants have been studied so as to disperse the waterinsoluble colorant stably in the aqueous medium.
However, regarding a conventional dispersant, it is difficult to disperse the water-insoluble colorant stably in the aqueous medium. Particularly, there was a problem that the colorant is aggregated at the time of storing ink for a long period of time or it becomes impossible to jet ink stably because an orifice (e.g. nozzle, etc.) of an ink-jet printer is clogged with ink.